TiO2-modified porphyrin-based covalent organic frameworks for efficient catalytic CO2 conversion to cyclic carbonates

Carbon dioxide (CO2) is a potent greenhouse gas and a rapid increase in CO2 concentration has become a major environmental hazard. The chemical fixation of CO2 to produce value-added products is the most fascinating and sustainable approach to overcome this global issue. In the present study, a TiO2-modified porphyrin-based covalent organic framework (COF) has been synthesized through the formation of imine bonds between the amino groups of meso-tetra(4-aminophenyl) porphyrin cobalt(ii) and aldehyde groups of 2,6-pyridine dicarboxaldehyde. The resulting covalent organic framework (CoPTi) was characterized using various techniques, including FTIR, powder-XRD, XPS, SEM, TGA, and BET. The synthesized catalyst exhibited >99% selectivity for cyclic carbonate formation with different functionalized epoxides in high yields under solvent-free conditions and at 1 atm CO2 pressure. Furthermore, the catalyst showed excellent performance in gram-scale reactions and retained its reusability without any loss in efficiency and selectivity for three cycles.